Myoadenylate deaminase deficiency: an enzyme defect in search of a disease

The frequency of MAD deficiency in cases with exercise intolerance compared with the frequency in series of consecutive muscle biopsies suggests a relation between the deficiency and exercise intolerance. Deficiency cases can be presumed by an impaired NH3 production during ischaemic exercise. The ischaemic exercise test also gives information concerning the familial character of the deficiency.